Frequency doubling and parametric fluorescence in a four-port aluminum gallium arsenide photonic chip.

In this Letter, we report on the fabrication and characterization of a monolithic III-V semiconductor photonic chip, designed to perform nonlinear parametric optical processes for frequency conversion and non-classical state generation. This chip co-integrates an AlGaAs microdisk that is evanescently coupled to two distinct suspended waveguides designed for light injection and collection around 1600 nm and 800 nm, respectively. Quasi-phase matching provided by the resonator geometry and material symmetry, resonant field enhancement, and confinement ensure efficient nonlinear interactions. We demonstrate second-harmonic generation efficiency of 5%W-1 and a biphoton generation rate of 1.2 kHz/µW through spontaneous down-conversion.

Direct Bell states generation on a III-V semiconductor chip at room temperature.

We demonstrate the direct generation of polarization-entangled photon pairs at room temperature and telecom wavelength in an AlGaAs semiconductor waveguide. The source is based on spontaneous parametric down-conversion with a counterpropagating phase-matching scheme. The quality of the two-photon state is assessed by the reconstruction of the density matrix giving a raw fidelity to a Bell state of 0.83; a theoretical model, taking into account the experimental parameters, provides ways to understand and control the amount of entanglement. Its compatibility with electrical injection, together with the high versatility of the generated two-photon state, make this source an attractive candidate for completely integrated quantum photonics devices.

Two-photon interference with a semiconductor integrated source at room temperature.

We experimentally demonstrate an integrated semiconductor ridge microcavity source of counterpropagating twin photons at room temperature in the telecom range. Based on type II parametric down conversion with a counterpropagating phase-matching, pump photons generate photon pairs with an efficiency of about 10(-11) and a spectral linewidth of 0.3 nm for a 1 mm long sample. The indistiguishability of the photons of the pair is measured via a Hong-Ou-Mandel two-photon interference experiment showing a visibility of 85 %. This work opens a route towards new guided-wave semiconductor quantum devices.

Surface plasmon quantum cascade lasers as terahertz local oscillators.

We characterize a heterodyne receiver based on a surface-plasmon waveguide quantum cascade laser (QCL) emitting at 2.84 THz as a local oscillator, and an NbN hot electron bolometer as a mixer. We find that the envelope of the far-field pattern of the QCL is diffraction-limited and superimposed onto interference fringes, which are similar to those found in narrow double-metal waveguide QCLs. Compared to the latter, a more directional beam allows for better coupling of the radiation power to the mixer. We obtain a receiver noise temperature of 1050 K when the mixer is at 2 K, which, to our knowledge, is the highest sensitivity reported at frequencies beyond 2.5 THz.